1. Field of the Invention
The present invention relates to a poly-insulator-poly (PIP) capacitor structure combined with a bipolarjunction transistor (BJT), an input RC circuit and the method for forming the two. In particular, the present invention relates to a poly-insulator-poly capacitor structure integrated with a bipolar junction transistor, a tunable input RC circuit and the method for forming the two.
2. Description of the Prior Art
In the conventional metal-oxide-semiconductor (MOS) process, capacitor structures are optionally formed to match the circuit design of the elements. Such capacitor structures are usually a metal-insulator-metal (MIM) capacitor or a metal-insulator-Si capacitor (MIS) capacitor.
Although the MIM capacitor or the MIS capacitor has been used in the traditional MOS process for a long time and is somewhat advantageous, neither the MIM capacitor set nor the MIS capacitor set can provide a code option. Another possible capacitor structure is called poly-insulator-poly (PIP) capacitor. So far, no capacitor has been used in the bipolar complementary metal-oxide-semiconductor (BiCMOS) process.
Accordingly, it is still needed to obtain a novel poly-insulator-poly capacitor structure integrated with a bipolar junction transistor made by the conventional bipolar complementary metal-oxide-semiconductor process. In one aspect, it provides a code option to form a capacitor array or a tunable code array, and in another aspect, it is still compatible with the conventional bipolar complementary metal-oxide-semiconductor process to simplify the process and to lower the cost for manufacturing the poly-insulator-poly capacitor structure integrated with the bipolar junction transistor.